package com.example.androidexample.viewpager;

import android.util.Log;
import android.view.View;

import androidx.viewpager.widget.ViewPager;

public class ZoomOutPageTransformer implements ViewPager.PageTransformer {

    private static final String TAG = "ZoomOutPageTransformer";

    private static final float MIN_SCALE = 0.8f;
    private static final float MIN_ALPHA = 0.5f;

    private static float defaultScale = 1f;

    public void transformPage(View view, float position) {
        Log.d(TAG, "transformPage: " + position + " view.tag = " + view.getTag());
        int pageWidth = view.getWidth();
        int pageHeight = view.getHeight();

        if (position < -1) { // [-Infinity,-1)
            // This page is way off-screen to the left.
            view.setAlpha(MIN_ALPHA);
            view.setScaleX(MIN_SCALE);
            view.setScaleY(MIN_SCALE);
        } else if (position <= 1) { // [-1,1]
            // Modify the default slide transition to shrink the page as well
            float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
//            float vertMargin = pageHeight * (1 - scaleFactor) / 2;
//            float horzMargin = pageWidth * (1 - scaleFactor) / 2;
//            if (position < 0) {
//                view.setTranslationX(horzMargin - vertMargin / 2);
//            } else {
//                view.setTranslationX(-horzMargin + vertMargin / 2);
//            }

            // Scale the page down (between MIN_SCALE and 1)
            view.setScaleX(scaleFactor);
            view.setScaleY(scaleFactor);

            // Fade the page relative to its size.
            float alphaFactor = Math.max(MIN_ALPHA, 1 - Math.abs(position));
            view.setAlpha(alphaFactor);

        } else { // (1,+Infinity]
            // This page is way off-screen to the right.
            view.setAlpha(MIN_ALPHA);
            view.setScaleX(MIN_SCALE);
            view.setScaleY(MIN_SCALE);
        }
    }
}